Flow control valves of the type having a liquid pressure actuated diaphragm to control opening and closing of a valve are known. Said control valves can be of the pilot valve operated type or be manually operated.
Background flow control valve patents are U.S. Pat. Nos. 3,439,895; 4,301,992; 4,336,918; and 4,508,136. These patents in turn refer to other patents and valve assemblies.